In order to improve the effectiveness and functionality of wound dressings and surgical implants, various attempts have been made to incorporate them with a variety of medicaments such as antibiotics, analgesics, and the like.
Examples of antibacterial wound dressings are disclosed in U.S. Pat. No. 4,191,743 to Klemm et al. , U.S. Pat. No. 2,804,424 to Stirn et al., and U.S. Pat. No. 2,809,149 to Cusumano. Similarly, U.S. Pat. No. 3,987,797 to Stephenson discloses a suture rendered antimicrobial.
Dressings which attempt to promote wound healing are disclosed in U.S. Pat. No. 5,124,155 to Reich. Most prior art surgical bandages and dressings which incorporate medications are made by soaking the material in an aqueous solution of the medicine. This can render the carrier brittle and inflexible upon drying. Moreover, it is difficult to control the rate of release of the medicament, or its effect on peripheral tissues, when it is applied to the carrier dissolved in a liquid state. Also, many important medicines are water insoluble and cannot be applied by this technique. Alternatively, the medicament is applied to the dressing or implant as a powder or dust which is quickly released and possesses a danger that large drug particles may irritate tissue or enter the circulatory system where they can block capillaries.
In addition to externally applied dressings, it is also known to impregnate an implantable surgical material with a medicament. For example, U.S. Pat. No. 5,197,977 to Hoffman Jr. et al. disclose a synthetic vascular graft that is impregnated with collagen and a medicament.
Additionally, Boyes-Varley et al. in Int.J. and Maxillafac. Surg. 1988; 17:138-141, describe the use in an animal study of a the Gelfoam.RTM. brand sponge with a saline solution of medicaments. However, the Physicians' Desk Reference, (Medical Economics, Co., Oradell, N.J.) 1992 edition warns that "it is not recommended that Gelfoam.RTM. be saturated with an antibiotic solution or dusted with antibiotic powder." A similar warning is provided with the entry of another popular surgical implant--the Surgicel.RTM. brand absorbable hemostat--which states that "the Surgicel.RTM. hemostat should not be impregnated with anti-infective agents."
It would be desirable to have a method for safely and effectively impregnating externally applied dressings as well as implantable sponges and hemostats, especially the popular Gelfoam.RTM. and Surgicel.RTM. brands. More particularly, it would be desirable to impregnate the dressings or implants with medicament in neither a solute nor a powder form, but a form which permits the drug concentration and release rate to be controlled.